Method for producing hat-shaped steel sheet pile

ABSTRACT

To suppress a material amount deficiency in arm parts which occurs at a rough shaping stage to produce a hat-shaped steel sheet pile product in a good shape when a large-size hat-shaped steel sheet pile is produced using a raw material in a rectangular cross-sectional shape (slab). A production method for producing a hat-shaped steel sheet pile by reducing a rectangular cross-sectional raw material, includes: edging rolling of performing reduction in a width direction on the rectangular cross-sectional raw material; and a first forming rolling of performing reduction in which a cross section of a material to be rolled after the edging rolling is formed into a substantially hat-shaped cross-sectional shape, wherein in the edging rolling, reduction in which a thickness of end parts in the width direction of the material to be rolled is increased using an edging caliber being a restraining caliber having a caliber bottom width T3 larger than a thickness T1 of the rectangular cross-sectional raw material to form into a dog-bone shape is performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2018-149325, filed in Japan onAug. 8, 2018, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a production method for producing ahat-shaped steel sheet pile from a rectangular cross-sectional rawmaterial.

BACKGROUND ART

Conventionally, production of a steel sheet pile having joints at bothends of a hat shape, a U shape, or the like is performed by a caliberrolling method. Known as a general process of the caliber rolling methodis first heating a raw material to a predetermined temperature in aheating furnace and sequentially rolling the raw material by a roughrolling mill, an intermediate rolling mill, and a finish rolling millincluding calibers.

According to the above-described general caliber rolling method, adomestically produced steel sheet pile product can be produced from araw material in a rectangular cross-section in status quo. Concretely,for example, a hat-shaped steel sheet pile product called a 10H producthaving a cross-section second moment per 1 m of a wall width of 1.0 (10⁴cm⁴/m) and a hat-shaped steel sheet pile product called a 25H producthaving a cross-section second moment per 1 m of a wall width of 2.5 (10⁴cm⁴/m) are produced by the conventionally known general caliber rollingmethod.

As a technique of producing a steel sheet pile from a rectangularcross-sectional raw material or a raw material similar thereto, varioustechnologies have been conceived. For example, Patent Document 1discloses a technique of using a beam blank material for H-shaped steelto produce a U-shaped steel sheet pile. Further, for example, PatentDocument 2 discloses a technique of using a rectangular slab as a rawmaterial to form the raw material into a suitable shape (predeterminedwidth and thickness) with a box caliber, thereby stabilizing biting at asubsequent process. Besides, for example, Patent Document 3 discloses atechnique of increasing caliber restraining force by using a rectangularslab as a raw material and using a deformed box caliber on the rawmaterial to prevent biting-out, improve a centering property, and thelike.

Besides, for example, Patent Document 4 discloses a technique ofperforming such width reduction as forms a local bulge on a slab surfacein order to form a protruding ridge on a joint of a steel sheet pile inproducing a steel sheet pile having a large effective width. Further,for example, Patent Document 5 discloses a technique of suppressing ashape defect at an end part of a material to be rolled in production ofa steel sheet pile.

PRIOR ART DOCUMENT Patent Document

[Patent Document 1] Japanese Laid-open Patent Publication No. H10-192905

[Patent Document 2] Japanese Laid-open Patent Publication No. H09-182901

[Patent Document 3] Japanese Laid-open Patent Publication No. H10-113707

[Patent Document 4] Japanese Laid-open Patent Publication No.2005-144497

[Patent Document 5] International Publication Pamphlet No. WO2018/139521 A1

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In recent years, accompanying an increase in size of building structuresor use for offshore structures, production of a hat-shaped steel sheetpile product with a size larger as compared with conventional ones isrequired, and in particular, a product having the full width and heightlarger as compared with those of the conventional ones is desired.According to studies of the present inventors, it has been found thatthere are various problems when such a large-size hat-shaped steel sheetpile is produced from a rectangular cross-sectional raw material(hereinafter, also called a slab).

For example, when the large-size hat-shaped steel sheet pile isproduced, the rectangular cross-sectional raw material is also requiredto increase its size, and when such a large-size rectangularcross-sectional raw material is formed, the increase in size of the rawmaterial causes a problem such as a material amount deficiency in a partof a cross section of the material to be rolled, resulting in that thereis a possibility of failing to produce a product in a desired shape.Concretely, an amount of deformation at a time of bending deformationincreases, or a bending moment arm being a starting point of the bendingdeformation extends to make the bending deformation superior to sheardeformation, and thus there is the possibility of causing the materialamount deficiency (metal deficiency) in a part of the cross section ofthe material to be rolled. In particular, metal in end surface parts ofthe rectangular cross-sectional raw material is drawn into a middle partthereof, resulting in that there is a possibility that metal in portionsbeing arm parts of the hat-shaped steel sheet pile later is deficient.

Note that the “large-size hat-shaped steel sheet pile” in thisdescription means, for example, a steel sheet pile product havingdimensions exceeding product dimensions of 900 mm in effective width and300 mm in effective height (so-called 25H product).

Regarding such problems, because the technique described in the abovePatent Document 1 targets the U-shaped steel sheet pile having no armpart, and adopts a configuration to deform portions in each of which athickness is increased in a dog-bone shape into flange parts, there isno reference to the metal deficiency in the portions being the armparts. Besides, the technique described in the above Patent Document 1,to begin with, does not adopt a technical idea such that a steel sheetpile is produced using a raw material in a rectangular cross-sectionalshape (slab), and thus there is no room for occurrence of the problemsuch as the material amount deficiency in the end surface parts of therectangular cross-sectional raw material as described above.

Besides, because the technique described in the above Patent Document 2is a technique according to production of a U-shaped steel sheet pilehaving no arm part despite performing such shaping as to match amaterial to be rolled with a shape of an upper roll to stabilize thebiting in a caliber, there is no reference to the problem such as thematerial amount deficiency in the end surface parts of the rectangularcross-sectional raw material as described above at a time of the biting,and the problem is not even suggested.

Besides, the technique described in the above Patent Document 3 pointsat an improvement in rolling stability such as the improvement in thecentering property by increasing restraining force with caliber contactin the box caliber being surface contact. However, also in the abovePatent Document 3, there is no reference to the problem such as thematerial amount deficiency in the end surface parts of the rectangularcross-sectional raw material.

Besides, the technique described in the above Patent Document 4discloses the effect of performing such width reduction as forms thelocal bulge on the slab surface in order to form the protruding ridge onthe joint of the steel sheet pile in producing the steel sheet pilehaving a large effective width. However, the technique of the abovePatent Document 4 aims at forming the protruding ridge, and there is noreference to the problem such as the material amount deficiency in theend surface parts of the rectangular cross-sectional raw material asdescribed above, and the problem is not even suggested.

Further, the technique described in the above Patent Document 5discloses a technique of suppressing the shape defect of a bite end partat a rough rolling step in production of the steel sheet pile to improveproductivity. Patent Document 5 refers to bulging deformation of a slabin edging rolling, and gives an explanation that the bulging deformationis a factor that facilitates the shape defect at the bite end part, andnaturally, there is no reference to the problem regarding the materialamount deficiency in the end surface parts of the rectangularcross-sectional raw material and means for solving the problem.

In view of the above circumstance, an object of the present invention isto provide a technique which makes it possible to suppress a materialamount deficiency in arm parts which occurs at a rough shaping stage toproduce a hat-shaped steel sheet pile product in a good shape when alarge-size hat-shaped steel sheet pile is produced using a raw materialin a rectangular cross-sectional shape (slab).

Means for Solving the Problems

To achieve the above object, according to the present invention, thereis provided a production method for producing a hat-shaped steel sheetpile by reducing a rectangular cross-sectional raw material, theproduction method including: edging rolling of performing reduction in awidth direction on the rectangular cross-sectional raw material; and afirst forming rolling of performing reduction in which a cross sectionof a material to be rolled after the edging rolling is formed into asubstantially hat-shaped cross-sectional shape, wherein in the edgingrolling, reduction in which a thickness of end parts in the widthdirection of the material to be rolled is increased using an edgingcaliber being a restraining caliber having a caliber bottom width T3larger than a thickness T1 of the rectangular cross-sectional rawmaterial to form into a dog-bone shape is performed.

In the edging rolling, a range Wa in which a thickness is increased inthe width direction of the rectangular cross-sectional raw material maybe set as a range corresponding to a part or a whole of a width Wb of aportion corresponding to an arm of the material to be rolled in thefirst forming rolling.

In the edging rolling, the range Wa in which a thickness is increased inthe width direction of the rectangular cross-sectional raw material maybe defined by a portion having a thickness larger than the caliberbottom width T3 of the edging caliber, and a relation between the rangeWa in which a thickness is increased in the width direction of therectangular cross-sectional raw material and the width Wb of the portioncorresponding to the arm of the material to be rolled in the firstforming rolling may satisfy Wa≤Wb.

Effect of the Invention

According to the present invention, it is possible to suppress amaterial amount deficiency in arm parts which occurs at a rough shapingstage to produce a hat-shaped steel sheet pile product in a good shapewhen a large-size hat-shaped steel sheet pile is produced using a rawmaterial in a rectangular cross-sectional shape (slab).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A schematic explanatory view of a rolling line according to anembodiment of the present invention.

FIG. 2 A schematic explanatory view of the caliber shape of a firstcaliber.

FIG. 3 A schematic explanatory view of the caliber shape of a secondcaliber.

FIG. 4 A schematic explanatory view of the caliber shape of a thirdcaliber.

FIG. 5 A schematic explanatory view of the caliber shape of a fourthcaliber.

FIG. 6 A schematic explanatory view of the caliber shape of a fifthcaliber.

FIG. 7 A schematic explanatory view of the caliber shape of a sixthcaliber.

FIG. 8 A schematic explanatory view illustrating a depressed height Hwith respect to a raw material and a bending deformation moment arm L inthe second caliber (first forming caliber).

FIG. 9 Schematic explanatory views illustrating conditions of reductionof the raw material in the second caliber (first forming caliber).

FIG. 10 Partially enlarged views of FIG. 9.

FIG. 11 A chart obtained by converting changes of a full width of uppersurface t1 and a full width maximum t2 of the raw material into numeralsby FEM analysis when rolling and shaping of the raw material in thesecond caliber (first forming caliber) is performed in a plurality ofpasses.

FIG. 12 Schematic views when edging rolling is performed on the rawmaterial to increase a thickness of end parts in a width direction.

FIG. 13 Schematic explanatory views comparing a cross section in therolling and shaping in the second caliber (first forming caliber) whenthe thickness of the end part in the width direction of the raw materialin the edging rolling according to the present invention is increased,and, a cross section in the rolling and shaping in the second caliber(first forming caliber) when the raw material has a conventionalrectangular cross-section as it is.

FIG. 14 A schematic view comparing cross-sectional shapes of materialsto be rolled at a time of completion of the rolling and shaping in thesecond caliber (first forming caliber).

FIG. 15 A chart obtained by converting changes of full widths of uppersurfaces t1 and full width maximums t2 of raw materials into numerals byFEM analysis when the rolling and shaping of the raw materials in thesecond caliber K2 (first forming caliber) is performed in a plurality ofpasses after the edging rolling is performed on slabs each having awidth larger than a width of the second caliber (first forming caliber)to increase a thickness of end parts in a width direction of the rawmaterial.

FIG. 16 An explanatory view regarding biting-out.

Embodiments for Carrying Out the Invention

Hereinafter, an embodiment of the present invention will be explainedreferring to the drawings. Note that, in this description and thedrawings, the same codes are given to components having substantiallythe same functional configurations to omit duplicated explanation. Notethat the explanation will be made illustrating a case of rolling andshaping a hat-shaped steel sheet pile in an upward open state (so-calledU-shaped posture) regarding production of a steel sheet pile product inthis embodiment.

Besides, in this embodiment, a material having a rectangularcross-section (so-called slab) is called a raw material B and a materialto be rolled made by reducing the raw material B into a substantiallyhat-shaped cross-sectional shape is called a material to be rolled A forconvenience of explanation. More specifically, steel materials in thesubstantially hat-shaped cross-sectional shape to be passed on a rollingline S are generically called a material to be rolled A, and portions ofthe material to be rolled A are described by different names mentionedbelow. Here, in this description, in the raw material B in therectangular cross-section, a long side direction of the rectangularcross-section is set as a width direction, and a short side directionthereof is set as a thickness direction. Besides, the material to berolled A is composed of a web corresponding part 3 corresponding to aweb of a hat-shaped steel sheet pile product, flange corresponding parts4, 5 connected to both end parts of the web corresponding part 3respectively, arm corresponding parts 6, 7 formed at tip ends of theflange corresponding parts 4, 5 respectively, and joint correspondingparts 8, 9 formed at tip ends of the arm corresponding parts 6, 7.

(Outline of Production Line)

FIG. 1 is an explanatory view of the rolling line S for producing thehat-shaped steel sheet pile being a rolling facility according to theembodiment of the present invention, and rolling mills provided on therolling line S. As illustrated in FIG. 1, on the rolling line S, a roughrolling mill (BD) 11, an intermediate rolling mill (R) 12, and a finishrolling mill (F) 14 are arranged in order. The rolling line S iscomposed of a plurality of lines S1 to S3, in which the line S1 and theline S2 are adjacent to each other and the line S2 and the line S3 areadjacent to each other. The lines S1 to S3 are coupled in series topartially overlap each other, and configured such that the material tobe rolled A is translated from S1 to S2 or S2 to S3 in a width directionthereof to thereby proceed on the rolling line S.

Further, as illustrated in FIG. 1, the rough rolling mill 11 is arrangedon the line S1, the intermediate rolling mill 12 is arranged on the lineS2, and the finish rolling mill 14 is arranged on the third line S3. Thelines S1 to S3 are configured to be capable of performing rolling withdifferent materials to be rolled A placed thereon respectively, and tobe capable of performing rolling of a plurality of materials to berolled A simultaneously in parallel on the rolling line S.

On the rolling line S illustrated in FIG. 1, a raw material having arectangular cross-sectional shape (the raw material B, the latermaterial to be rolled A) heated in a not-illustrated heating furnace issequentially rolled in the rough rolling mill 11 to the finish rollingmill 14 to form into a hat-shaped steel sheet pile being a finalproduct. In other words, a rough rolling step, an intermediate rollingstep, and a finish rolling step are performed in this order on the rawmaterial B (the material to be rolled A) to thereby produce a finalproduct.

(Outline of Each Caliber Configuration)

Hereinafter, configurations of calibers engraved in the rough rollingmill 11, the intermediate rolling mill 12, and the finish rolling mill14 arranged on the rolling line S (hereinafter, a plurality of rollingmills are also sometimes described in an abbreviation manner such as therough rolling mill 11 to the finish rolling mill 14) will be brieflyexplained referring to the drawings in order from the upstream of therolling line S. Note that since the above-described rough rolling mill11, intermediate rolling mill 12, and finish rolling mill 14 areconventionally generally used facilities excluding detailed shapes andconfigurations of the calibers, attention is focused on explanation ofthe configurations of the calibers but explanation of the detailedfacility configurations and so on of the rolling mills is omitted in thefollowing explanation in this description.

Further, calibers explained below referring to FIG. 2 to FIG. 7 areengraved in the rolling mills of the rough rolling mill 11 to the finishrolling mill 14, and which rolling mill each of the calibers explainedbelow is engraved in can be appropriately changed usually depending onthe conditions such as a facility status, product dimensions, and so onin consideration of the productivity (efficiency and yields) andworkability. Hence, the calibers are called a first caliber K1 to asixth caliber K6 in this embodiment, and the calibers will be explainedas those which may be engraved in order from the upstream side of therolling line S. Note that the shapes of the raw material B and thematerial to be rolled A which are to be reduced and shaped in thecalibers are illustrated by a one-dotted chain line for reference inFIG. 3 to FIG. 9.

However, the configurations of the first caliber K1 to the sixth caliberK6 according to this embodiment explained below are not limited to theillustrated forms, but, for example, the increased/decreased arrangementof correction calibers for various calibers can be appropriately changedaccording to the conditions such as a facility status, productdimensions, and so on. Note that in the first caliber K1 to the sixthcaliber K6 explained below, rolling and shaping of the material to berolled is desired to be the shaping in one pass for each of thecalibers, but, particularly at the rough rolling step, due to constraintof a biting property and a load characteristic, may be performed inreverse rolling (reversing rolling) in a plurality of passes, and thenumber of passes can be arbitrarily set according to characteristics ofthe rolling mills, or the like.

FIG. 2 is a schematic explanatory view of the caliber shape of the firstcaliber K1. As illustrated in FIG. 2, the first caliber K1 is a boxcaliber composed of an upper caliber roll 20 a and a lower caliber roll20 b, and caliber bottoms of the box caliber are in predeterminedtapered shapes. The first caliber K1 imparts the tapered shapes to shortside parts at end parts in the width direction of the raw material B ina rectangular cross-sectional shape and performs light reduction(so-called edging rolling) in the width direction in a state where thenot-illustrated raw material B in a rectangular cross-sectional shape ismade to stand up (a state of setting the width direction of a steelsheet pile in the vertical direction) in order to make a uniform widthdimension in the longitudinal direction. The light reduction here isperformed at a reduction amount of the degree to which dimensionvariations of the raw material B during casting, or the like arecorrected. Note that the reason why the tapered shapes are imparted tothe end parts in the width direction of the raw material B in arectangular cross-sectional shape is to cause the raw material B topreferably bites into the caliber shape of the later-described secondcaliber K2, and to stably perform desired reduction. In other words, the“tapered shape” here means such a shape of a caliber bottom surface ascan impart a gentle-slop shape to the end parts in the width directionof the not-illustrated raw material B through the light reduction. Thefirst caliber K1 illustrated in FIG. 2 is a caliber that performsso-called edging rolling, and the first caliber K1 is called an “edgingcaliber”.

Besides, FIG. 3 is a schematic explanatory view of the caliber shape ofthe second caliber K2. As illustrated in FIG. 3, the second caliber K2is composed of an upper caliber roll 30 a as a projection roll and alower caliber roll 30 b as a groove roll. The second caliber K2 performsreduction on the whole raw material B (the later material to be rolledA) in a rectangular cross-sectional shape subjected to the edgingrolling in the above first caliber K1. Here, the raw material B is in astate of being made to stand up in the reduction in the above firstcaliber K1, and the raw material B is thereafter rotated 90° or 270° andsubjected to reduction in the second caliber K2 in a state where thewidth direction of the raw material B is set in the horizontal direction(a state of setting the width direction of the steel sheet pile in thehorizontal direction), whereby rolling and shaping is performed to forma cross section from the rectangular cross-sectional shape into thesubstantially hat-shaped cross-sectional shape. Note that in thisdescription, the second caliber K2 is also called a “first formingcaliber” which performs a first forming rolling. The substantiallyhat-shaped cross-sectional shape here means a cross-sectional shape madeby performing reduction to such a degree that the raw material B hasclear boundaries of a portion corresponding to a web (web correspondingpart 3), portions corresponding to flanges (flange corresponding parts4, 5), and portions corresponding to arms (arm corresponding parts 6,7), and does not always mean the cross-sectional shape shaped up to fineshapes such as joint shapes and so on.

The upper caliber roll 30 a is composed of a web facing part 32 facingthe upper surface of the web corresponding part 3 of the raw material B,flange facing parts 34, 35 facing the upper surfaces of the flangecorresponding parts 4, 5, and arm facing parts 37, 38 facing the uppersurfaces of the arm corresponding parts 6, 7.

On the other hand, the lower caliber roll 30 b is composed of a webfacing part 42 facing the lower surface of the web corresponding part 3of the raw material B, flange facing parts 44, 45 facing the lowersurfaces of the flange corresponding parts 4, 5, and arm facing parts47, 48 facing the lower surfaces of the arm corresponding parts 6, 7.

Further, FIG. 4 is a schematic explanatory view of the caliber shape ofthe third caliber K3. As illustrated in FIG. 4, the third caliber K3 iscomposed of an upper caliber roll 50 a as a projection roll and a lowercaliber roll 50 b as a groove roll. The third caliber K3 performsfurther reduction on the material to be rolled A subjected to theshaping in the second caliber K2 to roughly form the joint shapestogether, and performs, on the whole material to be rolled A, reductionto form the cross-sectional shape from the substantially hat-shapedcross-section shape into the substantially hat-shaped cross-sectionalshape formed with joint parts. In this description, the third caliber K3is also called a “second forming caliber” which performs a secondforming rolling.

The upper caliber roll 50 a is composed of a web facing part 52 facingthe upper surface of the web corresponding part 3 of the material to berolled A, flange facing parts 54, 55 facing the upper surfaces of theflange corresponding parts 4, 5, and arm facing parts 57, 58 facing theupper surfaces of the arm corresponding parts 6, 7.

Further, the lower caliber roll 50 b is composed of a web facing part 62facing the lower surface of the web corresponding part 3 of the materialto be rolled A, flange facing parts 64, 65 facing the lower surfaces ofthe flange corresponding parts 4, 5, and arm facing parts 67, 68 facingthe lower surfaces of the arm corresponding parts 6, 7.

FIG. 5 is a schematic explanatory view of the caliber shape of thefourth caliber K4. As illustrated in FIG. 5, the fourth caliber K4 iscomposed of an upper caliber roll 70 a as a projection roll and a lowercaliber roll 70 b as a groove roll. The fourth caliber K4 performsfurther forming of the joint shapes and performs thickness reduction andforming (thickness drawing rolling) on the whole material to be rolledA, which is formed into a shape closer to the hat-shaped steel sheetpile product.

FIG. 6 is a schematic explanatory view of the caliber shape of the fifthcaliber K5. As illustrated in FIG. 6, the fifth caliber K5 is composedof an upper caliber roll 100 a as a projection roll and a lower caliberroll 100 b as a groove roll. The fifth caliber K5 reduces a platethickness to a thickness corresponding to that of a final product andperforms rolling which decides a substantial plate thickness of theproduct. Besides, also regarding shapes of joint corresponding parts 8,9 (hereinafter, joint shapes), rolling which decides a plate thicknessof the joint is performed, and this almost decides a final product shapeincluding the joint shapes. In more detail, the fifth caliber K5performs the plate-thickness decision on the joint shapes, and thelater-described sixth caliber K6 performs bending forming of the jointcorresponding parts 8, 9. Note that the fifth caliber K5 is smaller inthickness reduction amount than the fourth caliber K4 which activelyperforms the thickness reduction of the whole material to be rolled A.

FIG. 7 is a schematic explanatory view of the caliber shape of the sixthcaliber K6. As illustrated in FIG. 7, the sixth caliber K6 is composedof an upper caliber roll 110 a as a projection roll and a lower caliberroll 110 b as a groove roll, and the sixth caliber K6 performs bendingforming of the joint corresponding parts 8, 9 of the material to berolled A and shaping of the whole material to be rolled A by lightreduction rolling. Specifically, joint forming of bending the wholejoint corresponding parts 8, 9 into the joint shapes of the product isperformed. Thus, the sixth caliber K6 forms the material to be rolled Aup to the shape of the hat-shaped steel sheet pile product.

The caliber shapes and functions of the first caliber K1 to the sixthcaliber K6 have been explained above referring to FIG. 2 to FIG. 7. Asdescribed above, the caliber rolling method for the hat-shaped steelsheet pile includes the rough rolling step, the intermediate rollingstep, and the finish rolling step and, for example, the rough rollingstep and the intermediate rolling step are performed in sequence in thecalibers of the first caliber K1 to the fifth caliber K5, and the finishrolling step is performed in the sixth caliber K6. Here, all of thecaliber shapes of the fourth caliber K4 to the sixth caliber K6 are inthe substantially hat-shaped cross-sectional shape, and engraved inshapes closer to the product shape as they are calibers at later stages.In other words, the shape of the sixth caliber K6 where the finishrolling being the final step is performed is in the hat-shaped steelsheet pile product shape.

Note that the rough rolling mill (BD) 11, the intermediate rolling mill(R) 12, and the finish rolling mill (F) 14 are arranged in order on therolling line S in this embodiment, and the above-described first caliberK1 to sixth caliber K6 are dispersedly engraved in an arbitraryconfiguration in the rolling mills. One example can be a configurationin which the first caliber K1 to the third caliber K3 are engraved inthe rough rolling mill 11, the fourth caliber K4 and the fifth caliberK5 are engraved in the intermediate rolling mill 12, and the sixthcaliber K6 is engraved in the finish rolling mill 14. However, thecaliber configuration in the present invention is not limited to such aconfiguration.

(Problems at Rough Rolling Step)

The present inventors found problems as explained below regarding therolling and shaping in the first forming caliber corresponding to thesecond caliber K2 in this embodiment at the rough rolling step inproducing a hat-shaped steel sheet pile product having a larger sizethan conventional ones from the raw material B in the rectangularcross-sectional shape, and earnestly carried out studies on a techniquefor solving the problems.

Note that conventionally produced hat-shaped steel sheet pile productswere, for example, each a product equal to or less than a size of aproduct called a so-called 25H product such as 900 mm in effectivewidth×300 mm in effective height. In contrast with this, the presentinventors point at production of a product with such a size as exceeds900 mm in effective width×300 mm in effective height as the large-sizehat-shaped steel sheet pile product. In producing the product with sucha size, the problems as explained below are very remarkable, andimportant as problems that need to be solved.

First, because a height of a final product extends with an increase insize of the product, a rolling height in the second caliber K2 (firstforming caliber) extends. In other words, in the rolling and shaping inthe second caliber K2 (first forming caliber), a depressed height H withrespect to the raw material B extends to increase a bending deformationamount of the raw material B.

Second, because a width of the final product extends with the increasein size of the product, a bending deformation moment arm L in therolling and shaping in the second caliber K2 (first forming caliber)extends. Therefore, deformation in the rolling and shaping becomesdeformation such that bending deformation is superior to sheardeformation.

FIG. 8 is a schematic explanatory view illustrating a depressed height Hwith respect to the raw material B and a bending deformation moment armL in the second caliber K2 (first forming caliber). The depressed heightH illustrated in FIG. 8 indicates an amount to be reduced in a case ofperforming the rolling and shaping which forms a shape of the rawmaterial B into a substantially hat-shaped cross-sectional shape in thesecond caliber K2 (first forming caliber), and there is a tendency thatthe larger a height of a final hat-shaped steel sheet pile product is,the more the depressed height H also extends.

Further, the bending deformation moment arm L illustrated in FIG. 8 is amoment arm in performing bending deformation in order to form a flangecorresponding portion when a cross-sectional shape of the raw material Bis formed from the rectangular cross-sectional shape into thesubstantially hat-shaped cross-sectional shape in the second caliber K2(first forming caliber), and there is a tendency that the larger a widthof the final hat-shaped steel sheet pile product is, the more thebending deformation moment arm L also extends.

FIG. 9 are schematic explanatory views illustrating conditions ofreduction of the raw material B in the second caliber K2 (first formingcaliber), and the conditions of reduction are illustrated in stages of(a) to (c). Further, the cross section of the raw material B isillustrated by a one-dotted chain line, and FIGS. 10(a) to (c)illustrate partially enlarged views of FIG. 9 (dotted line portions inFIG. 9). As illustrated in FIG. 9, the rolling and shaping in the secondcaliber K2 (first forming caliber) can be indicated by being dividedmainly into three stages. As illustrated in FIGS. 9(a) to (b), at afirst stage, forming is performed in a state of bringing only acircumferential surface of a maximum diameter of the upper caliber roll30 a into contact with the raw material B, and the first stage is astage preceding a start of thickness reduction of portions B1corresponding to flanges of the raw material. At the first stage, theraw material B is not subjected to the thickness reduction, namely, theraw material B is only formed to be bent.

As illustrated in FIG. 9(b), a second stage indicates a condition fromthe start of the thickness reduction of the portions B1 corresponding tothe flanges of the raw material to a stage preceding a start ofthickness reduction of portions B2 corresponding to the arms of the rawmaterial and a portion B3 corresponding to the web of the raw material,after the end of the above-described first stage. At the second stage,before the reduction of the portions B2 corresponding to the arms, thethickness reduction of only the portions B1 corresponding to the flangesof the raw material is started.

As illustrated in FIG. 9(c), a third stage indicates a stage ofperforming the thickness reduction of the whole raw material B (B1 toB3) (reduction of the whole surface) after the end of theabove-described second stage.

In the rolling and shaping of being performed by being divided into theabove-described first stage to third stage, the first stage isconfigured to only form the raw material B to be bent without beingsubjected to the thickness reduction, and at that time, to bring thecircumferential surface of the upper caliber roll 30 a into contact withthe vicinity of the middle part of the raw material B (the portion B3corresponding to the web) and not to bring the circumferential surfaceof the upper caliber roll 30 a into contact with the other upper surfaceportion of the raw material B. In other words, at the first stage, thewhole raw material B is formed in an unrestrained state, and the uppersurface of the vicinity of the middle part thereof is pressed downwardby the upper caliber roll 30 a, to thus cause a drawing effect from theportions B2 corresponding to the arms of the raw material toward theportions B1 corresponding to the flanges and the portion B3corresponding to the web. This decreases a material amount of theportions B2 corresponding to the arms of the raw material, resulting inthat a phenomenon such as a material amount deficiency in the sectionsB2 is seen. This causes gap parts 121, 122 in the vicinity of both endparts of the second caliber K2 (first forming caliber) as illustrated inFIG. 9(b). Such gap parts 121, 122 also remain at the third stageillustrated in FIG. 9(c), and it is found that rolling and shaping at alater stage is adversely affected.

FIG. 11(a) is a chart obtained by converting changes of a full width ofupper surface t1 and a full width maximum t2 of the raw material B intonumerals by FEM analysis when rolling and shaping of the raw material Bin the second caliber 2K (first forming caliber) is performed in aplurality of passes. Further, FIG. 11(b) is an explanatory view of “fullwidth of upper surface”, “full width maximum”, and “web gap”. Note thatthe chart illustrated in FIG. 11(a) is the one when the rolling andshaping in the second caliber K2 (first forming caliber) is performed ina pass schedule described in Table 1 presented below by using a slab rawmaterial with cross-sectional dimensions of 1930 mm×300 mm. Here, asillustrated in FIG. 11(b), the “full width of upper surface t1” of theraw material B in the rolling and shaping is defined as a value of afull width decided in contact with the upper caliber roll 30 a, and the“full width maximum t2” is defined as a value of a full width decided incontact with the lower caliber roll 30 b.

TABLE 1 PASS WEB GAP 1 584 2 509 3 434 4 359 5 336 6 314 7 291 8 269 9246 10 224 11 201 12 179 13 161 14 144 15 128 16 111

As a premise, it is said to be in an ideal deformed state that thenumeric values of the full width of upper surface t1 and the full widthmaximum t2 have no difference and always coincide with each other.However, as illustrated in FIG. 11(a), with progress of the rolling andshaping passes in the second caliber K2 (first forming caliber), inparticular, the full width of upper surface t1 varies greatly, and forexample, a thickness deficiency occurs in a range of the degree of about50 mm from an end part in the final pass (the 16th pass in Table 1).This is attributed to the fact that the material amount of the portionsB2 corresponding to the arms decreases accompanying the rolling andshaping (forming) to cause the material amount deficiency as describedabove referring to FIGS. 9, 10.

Further, in the pass schedule presented in Table 1, in particular, avariation range (decrease range) is large during the passes up to astart of the thickness reduction of the portions B1 corresponding to theflanges (the first to fourth passes). This is because the first pass tothe fourth pass are at the stage where the raw material B is notsubjected to the thickness reduction but subjected to the bendingdeformation in addition to the shear deformation.

On the other hand, in an eighth and subsequent passes of the passschedule presented in Table 1, widening occurs due to the thicknessreduction of the portions B2 corresponding to the arms of the rawmaterial, and the full width of upper surface t1 turns to an increase,but the rolling and shaping in the second caliber K2 (first formingcaliber) is ended without completely eliminating the material amountdeficiency also in the final pass.

(Edging Rolling for Solving Problems and Operation and Effect Thereof)

As explained above referring to FIGS. 9 to 11, in producing thelarge-size hat-shaped steel sheet pile product, there occurs thematerial amount deficiency of the portions B2 corresponding to the armsin the rolling and shaping in the second caliber K2 (first formingcaliber), and as a result, there is a possibility of causing a shapedefect of a product accompanying the material amount deficiency in armparts of the product.

Thus, the present inventors earnestly carried out studies, and obtainedfindings that can eliminate the material amount deficiency of theportions B2 corresponding to the arms by rolling and shaping the rawmaterial B in a dog-bone shape after edging rolling and shaping in thesecond caliber K2 (first forming caliber), after using a rectangularcross-sectional raw material (slab) having a width larger than a caliberwidth of the second caliber K2 (first forming caliber) and performingrolling and shaping under predetermined conditions in the edging caliber(the first caliber K1 in this embodiment) being at a preceding stage ofthe second caliber K2 (first forming caliber). Hereinafter, the findingswill be explained referring to the drawings and so on.

Note that the “dog-bone shape” in this description means a state where athickness of both-side end parts in the width direction is deformed intoa larger shape relative to a middle part in the width direction ascompared with a rectangular cross-section, and means a rectangularcross-sectional raw material, what is called, deformed into a doublebulging shape.

FIG. 12 are schematic views when the edging rolling is performed on theraw material B having a width larger than that of the second caliber K2(first forming caliber) to increase the thickness of end parts in thewidth direction (upper and lower both end parts in the drawing) in theedging caliber. FIG. 12(a) illustrates a cross section of a material tobe rolled (raw material B) in the dog-bone shape, what is called,deformed into a double bulging shape, and FIG. 12(b) is the one obtainedby enlarging a part of the cross section. Concretely, as shown in theillustrations, a slab thickness is indicated with T1, and a restrainingcaliber such that a width of a caliber bottom surface (caliber bottomwidth) T3 is larger than the slab thickness T1 (namely, T1<T3) is usedas the edging caliber with respect to the raw material B having a widthlarger than a width of the second caliber K2 (first forming caliber).Then, in the edging caliber, by performing such edging rolling as makesa maximum thickness of the end parts in the width direction of the rawmaterial B to be T2, it is possible to suppress the material amountdeficiency of the portions B2 corresponding to the arms in the secondcaliber K2 (first forming caliber). Here, as illustrated in FIG. 12(b),the maximum thickness T2 of the raw material B after the edging rollingis set to be a value larger than those of both the slab thickness T1 andthe caliber bottom width T3 (T1<T3<T2).

Besides, in the width direction (vertical direction in FIG. 12) of theraw material B, when a range in which the thickness is increased morethan the slab thickness T1 is defined as Wa, the material amountdeficiency of the portions B2 corresponding to the arms in the secondcaliber K2 (first forming caliber) is suppressed by the edging rolling,while, from the viewpoint of prevention of metal extrusion (so-called“biting-out”) from the caliber due to a material amount excess, theabove-described range Wa is preferably set as a range corresponding to apart or the whole of a width Wb (illustrated in FIG. 13) of the portionB2 corresponding to the arm of the raw material in the second caliber K2(first forming caliber). In other words, the relation of Wa≤Wb ispreferably satisfied. This is attributed to the fact that, when therolling and shaping in the second caliber K2 (first forming caliber) isconsidered to be divided into the three stages, it is found that thedrawing effect occurs from the portions B2 corresponding to the arms ofthe raw material toward the portions B1 corresponding to the flanges andthe portion B3 corresponding to the web at the first stage, inparticular, it is found that the material amount of the portions B2corresponding to the arms of the raw material decreases to cause thephenomenon such as a material amount deficiency in the sections B2 atthe first stage, as described above referring to FIGS. 9, 10.

Note that in a case of measuring or defining the above values such asT1, T2, T3 and the ranges such as Wa, Wb, it is only necessary to, ateach corner part having a predetermined curvature of a calibercircumferential surface of the first caliber K1 or the second caliberK2, measure or define the dimensions using, as a reference, anintersection point when virtual lines are drawn on both-side portions ofthe corner part. For example, as illustrated in FIG. 12(b), in a case ofdefining the caliber bottom width T3 of the edging caliber, or in a caseof measuring the range Wa to increase the thickness, it is onlynecessary to use, as a reference, P1 being an intersection point ofextending virtual lines on a side surface and a bottom surface of theedging caliber.

Here, when such edging rolling as makes a maximum thickness of the endparts in the width direction to be T2 (>T1) is performed on the rawmaterial B having the slab thickness of T1 and having a width largerthan that of the second caliber K2 (first forming caliber), T2 and T1preferably have a predetermined relationship. It is desired that thepreferable relationship between T2 and T1 is preferably decided based onchanges in the full width of upper surface t1 and the full width maximumt2 of the raw material B described later referring to FIG. 15.

FIG. 13 are schematic explanatory views comparing a cross section in therolling and shaping in the second caliber K2 (first forming caliber)when the thickness of the end part in the width direction of the rawmaterial in the edging rolling according to the present invention isincreased, and, a cross section in the rolling and shaping in the secondcaliber K2 (first forming caliber) when the raw material has aconventional rectangular cross-section as it is, (a) is the crosssection in application of the present invention, and (b) is the crosssection in application of the conventional rectangular cross-section.Note that FIG. 13 are the cross sections in each starting the thicknessreduction of the portion B1 corresponding to the flange of the rawmaterial, (a) and (b) illustrate a state of having the same roll gap,and only a part of each of the cross sections is enlarged forconvenience of explanation.

As illustrated in FIG. 13(b), in the rolling and shaping of theconventional rectangular cross-section in the second caliber K2 (firstforming caliber), the reduction of the portion B2 corresponding to thearm is not started at the stage of starting the reduction of the portionB1 corresponding to the flange. On the other hand, as illustrated inFIG. 13(a), in the rolling and shaping in the second caliber K2 (firstforming caliber) in the application of the present invention, thereduction of the portion B2 corresponding to the arm is started atalmost the same timing as the stage of starting the reduction of theportion B1 corresponding to the flange, and the full width of uppersurface t1 turns to an increase due to the thickness reduction of thearm in subsequent deformation.

FIG. 14 is a schematic view comparing cross-sectional shapes of thematerials to be rolled at a time of completion of the rolling andshaping in the second caliber K2 (first forming caliber), a hatchingportion indicates the cross section in the application of the presentinvention, and a solid line indicated in a section surrounded by adotted line indicates a portion deficient in the material amount in theconventional cross section, and in particular, the vicinity of theportions B2 corresponding to the arms of the materials to be rolled isenlarged to be illustrated. As illustrated in FIG. 14, after applyingthe present invention and increasing the thickness of the end part inthe width direction of the raw material in the edging rolling, byperforming the rolling and shaping in the second caliber K2 (firstforming caliber), it is found that the material amount deficiency of theportion B2 corresponding to the arm is suppressed and eliminated (referto a dotted-line surrounded portion in FIG. 14).

Further, FIG. 15 is a chart obtained by converting changes of fullwidths of upper surfaces t1 and full width maximums t2 of raw materialsB into numerals by FEM analysis when the rolling and shaping of the rawmaterials B in the second caliber K2 (first forming caliber) isperformed in a plurality of passes after performing the edging rollingon slabs each having a width larger than a width of the second caliberK2 (first forming caliber) to increase the thickness of end parts in thewidth direction of the raw material. Note that FIG. 15 illustratesgraphs each of when the rolling and shaping in the second caliber K2(first forming caliber) is performed after performing the edging rollingon the slab having a width 100 mm larger than a width of the secondcaliber K2 (first forming caliber) (namely, 2030 mm×300 mm rawmaterial), and, when the rolling and shaping in the second caliber K2(first forming caliber) is performed after performing the edging rollingon the slab having a width 50 mm larger than a width of the secondcaliber K2 (first forming caliber) (namely, 1980 mm×300 mm rawmaterial), and also illustrates graphs (similar to graphs in FIG. 11) inthe case of no application of the present invention (conventionalmethod) together for reference purposes. Besides, the pass schedule ofthe rolling and shaping is the pass schedule described in theabove-described Table 1.

As illustrated in FIG. 15, it is perceived that when the rolling andshaping in the second caliber K2 (first forming caliber) is performedafter extending the width of each of the slabs to be used and increasingthe thickness of the portions corresponding to the arms in bulging bythe edging rolling, the increase in the thickness of the portionscorresponding to the arms brings deformation which promotes drawing ofmetal to flange sides in the passes at a preceding stage (for example,the first pass to the fifth pass), but as described above referring toFIG. 13 and so on, there is a tendency that a rise (recovery) of thefull width of upper surface t1 in the passes at a later stage (forexample, the sixth and subsequent passes) is remarkable because thereduction start of the portions corresponding to the arms isaccelerated. In particular, when the rolling and shaping in the secondcaliber K2 (first forming caliber) is performed after performing theedging rolling on the slab having a width 100 mm larger than a width ofthe second caliber K2 (first forming caliber), it is found that the fullwidth of upper surface t1 rises up to a value coinciding with a value ofthe full width maximum t2 in the final pass, to realize the recover ofthe material amount deficiency.

FIG. 15 describes the schedule in which the rolling and shaping isperformed in the total 16 passes (refer to Table 1), and an idealdeformed state in the final pass (the 16th pass) is a deformation suchthat the full width of upper surface t1 and the full width maximum t2coincide with each other (refer to the hatching portion in FIG. 14).

When a slab width is too large and a reduction amount in the edgingrolling is too much, metal extrudes from the caliber, so-call“biting-out” occurs, as in FIG. 16, which has a possibility of leadingto a defect such as a product flaw (refer to a dotted line portion inFIG. 16). Under the condition that the slab having a width 100 mm largerthan a width of the second caliber K2 (first forming caliber)illustrated in FIG. 15 is used, the material amount is excessive becausethe full width maximum t2< the full width of upper surface t1 isobtained in the final pass. On the other hand, under the condition thatthe slab having a width 50 mm larger than the width of the secondcaliber K2 (first forming caliber) illustrated in FIG. 15 is used, thefull width maximum t2> the full width of upper surface t1 is obtained inthe final pass, resulting in the material amount deficiency. It is foundfrom the results of the studies as above that a dimension condition ofan appropriate slab for realizing the ideal deformed state is acondition that a width of the slab is larger than the width of thesecond caliber K2 (first forming caliber) by more than 50 mm and lessthan 100 mm.

Note that it is only necessary for the width of the second caliber K2(first forming caliber) to be calculated based on product dimensions(particularly a product width) of the final hat-shaped steel sheet pileproduct, for example, to be defined as a width length obtained by addinga thickness portion of a joint part and a bent portion of the joint partto the product width.

As explained above referring to FIG. 12 to FIG. 16, by adopting themethod of performing the rolling and shaping of the raw material B inthe second caliber K2 (first forming caliber) after performing theedging rolling on the slab having a width larger than a width of thesecond caliber K2 (first forming caliber) to increase the thickness ofthe end parts in the width direction of the raw material, there issolved the problem that in producing the large-size hat-shaped steelsheet pile product, the material amount deficiency of the portions B2corresponding to the arms occurs in the rolling and shaping in thesecond caliber K2 (first forming caliber), resulting in causing theshape defect of the product accompanying the material amount deficiencyin the arm parts of the product. In other words, it becomes possible tostably produce a hat-shaped steel sheet pile product in a good shape.

In that case, when the thickness of the end parts in the width directionof the raw material is increased in the edging rolling, the range Wa inwhich the thickness is increased is preferably smaller than the width Wbof the portion B2 corresponding to the arm of the raw material in thesecond caliber K2 (first forming caliber). It is found that the materialamount deficiency in the arm parts of the product can be sufficientlyeliminated by satisfying the relation of Wa≤Wb.

One example of the embodiment of the present invention has beendescribed above, but the present invention is not limited to theillustrated embodiment. It should be understood that various changes andmodifications are readily apparent to those skilled in the art withinthe scope of the spirit as set forth in claims, and those should also becovered by the technical scope of the present invention.

In the above-described embodiment, as the configurations of the calibersengraved in the rolling mills, there is cited a configuration in whichthe first caliber K1 to the third caliber K3 are engraved in the roughrolling mill 11, the fourth caliber K4 and the fifth caliber K5 areengraved in the intermediate rolling mill 12, and the sixth caliber K6is engraved in the finish rolling mill 14, but the engraving of thecalibers in the respective rolling mills in the present invention can bearbitrarily decided.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a production method for producinga hat-shaped steel sheet pile from a rectangular cross-sectional rawmaterial.

EXPLANATION OF CODES

3 . . . web corresponding part

4, 5 . . . flange corresponding part

6, 7 . . . arm corresponding part

8, 9 . . . joint corresponding part

11 . . . rough rolling mill

12 . . . intermediate rolling mill

14 . . . finish rolling mill

32, 42 . . . web facing part (of second caliber)

34, 35, 44, 45 . . . flange facing part (of second caliber)

37, 38, 47, 48 . . . arm facing part (of second caliber)

A . . . material to be rolled

B . . . raw material

K1 to K6 . . . first caliber to sixth caliber

S (S1 to S3) . . . rolling line

What is claimed is:
 1. A production method for producing a hat-shapedsteel sheet pile by reducing a rectangular cross-sectional raw material,the production method comprising: edging rolling of performing reductionin a width direction on the rectangular cross-sectional raw material;and a first forming rolling of performing reduction in which a crosssection of a material to be rolled after the edging rolling is formedinto a substantially hat-shaped cross-sectional shape, wherein in theedging rolling, reduction in which a thickness of end parts in the widthdirection of the material to be rolled is increased using an edgingcaliber being a restraining caliber having a caliber bottom width T3larger than a thickness T1 of the rectangular cross-sectional rawmaterial to form into a dog-bone shape is performed.
 2. The productionmethod for the hat-shaped steel sheet pile according to claim 1, whereinin the edging rolling, a range Wa in which a thickness is increased inthe width direction of the rectangular cross-sectional raw material isset as a range corresponding to a part or a whole of a width Wb of aportion corresponding to an arm of the material to be rolled in thefirst forming rolling.
 3. The production method for the hat-shaped steelsheet pile according to claim 2, wherein in the edging rolling, therange Wa in which a thickness is increased in the width direction of therectangular cross-sectional raw material is defined by a portion havinga thickness larger than the caliber bottom width T3 of the edgingcaliber, and wherein a relation between the range Wa in which athickness is increased in the width direction of the rectangularcross-sectional raw material and the width Wb of the portioncorresponding to the arm of the material to be rolled in the firstforming rolling satisfies Wa≤Wb.